This invention relates to a gas range in general, and more particularly to a gas range wherein the cooking surface is constituted by a glass-ceramic plate.
Conventional gas ranges have burners that are provided with a plurality of apertures from which flames issue when the burner is in use. Usually, the apertures are arranged in form of one or more rings. The pots, pans or the like to be heated are placed on support frames or similar structures which hold them in such a position above the burner, that the hottest parts of the flames come in contact with the bottom wall of the respective cooking utensil.
Burners of this type have certain disadvantages. The direct contact of the flames with the utensil can lead to local overheating, and result in burning of the contents of the utensil. The utensil must be precisely oriented relative to the burner, as dictated by the location of the flames and of the support frame, and cannot be positioned in any other way. Also, the flames and the combustion gases contact the utensils directly and this leads to blackening of the utensil over a period of time, which blackening is at least difficult to remove and sometimes cannot be removed at all.
Other types of gas burners are already from other applications, i.e. from space heating, heating of industrial furnaces or the like. These are radiation heaters, where the gas burns substantially without development of a flame, at the surface of a perforated ceramic plate. Burners of this type are usually provided with mixing tubes, usually Venturi-tubes, which are connected with the combustion gas source. Nozzles admit the combustion gas into the mixing tube, and the air and oxygen required to support combustion are drawn by an injector effect into the mixing tube where they mix with the gas. This mixture then travels into a housing that carries one or more perforated ceramic plates at the exposed (i.e. outwardly facing) surfaces of which the combustion takes place, heating the ceramic plate so that the latter yields intensive radiated energy. This type of burner has not been used in gas ranges, because boiling over of food or accidental spilling of food, would cause the ceramic plates to become contaminated and to cease proper operations. Such plates cannot be cleaned in the ordinary household and their use was therefore impractical in gas ranges.
Also known from the art are glass-ceramic plates, i.e. plates of a glass-crystalline material which is obtained from a special glass by thermal after-treatment. Glass-ceramic of this type is, for example, manufactured by the Corning Glassworks and has very unusual and highly advantageous properties, such as:
THE LINEAR THERMAL COEFFICIENT IS EXPANSION IS ALMOST ZERO;
MAXIMUM OPERATING TEMPERATURE IS ABOUT 700.degree. C;
the material is completely without pores;
THE MATERIAL HAS EXCELLENT RESISTANCE TO CHEMICALS;
THE MATERIAL IS RATHER HARD AND THEREFORE RESISTANT TO WEAR, ESPECIALLY TO SCRATCHES;
THE MATERIAL IS VERY RESISTANT TO BREAKAGE AND ATTACK BY ACIDS, LYES, AND THE LIKE; AND
THE MATERIAL HAS FOOD RADIATION PERMEABILITY IN THE INFRA-RED RANGE AT WAVELENGTHS OF 0.4-5 MG.